Differential Hall-effect gear-tooth sensor module.Differential Hall-effect gear-tooth sensor module for two-wireapplications Allegro MicroSystems has introduced a new truezero-speed, self-calibrating, differential Hall-effect gear-toothsensor module for two-wire applications such as automotiveantilock braking systems (ABS).The new ATS640JSB sensor subassembly is a peak detectingdevice that uses internal gain control to provide extremely stableduty cycles down to zero speed.Each sensor subassembly consists of a high-temperature plasticshell that holds together a samarium-cobalt magnet, a pole piece,and a true zero-speed BiCMOS differential Hall-effect gear-toothsensor IC that has been optimised to the magnetic circuit. Thissmall package can be easily assembled and used in conjunctionwith a wide variety of gear shapes and sizes.The sensor incorporates a dual-element Hall IC that switches inresponse to differential magnetic signals created by a ferrous target.The sophisticated self-calibrating digital-processing circuitrynormalises the internal gain of the device to minimise the effectof air-gap variations and to reduce vibration sensitivity.The compensation circuitry eliminates magnet and system offsetssuch as those caused by tilt, yet provides zero-speed detectioncapabilities without the associated running jitter inherent in classicaldigital solutions.This new device is ideal for use in gathering speed, position, andtiming information using gear-tooth-based configurations. TheATS640JSB is particularly suited to those applications that requireextremely accurate duty-cycle control or accurate edge detection.The low vibration sensitivity also makes this device extremelyuseful for transmission speed sensing._____________________________________________More information from:Allegro MicroSystems Europe